The present invention relates generally to a magnetoresistance effect magnetic head that uses a magnetoresistance effect element. More particularly, the invention relates to biasing layers of a magnetoresistance effect magnetic head disposed at ends of the magnetoresistance effect element for improving reproduction of the signal magnetic field from a magnetic recording medium.
Referring now to FIG. 1, a magnetoresistance effect magnetic head 100 (hereinafter called the magnetic head), for example, is well known. FIG. 1 shows a cross-section of the overall structure of the magnetic head 100 as it faces the magnetic recording medium (not shown). A magnetoresistance effect element 101 for sensing the signal magnetic field from the magnetic recording medium, such as a hard disk, is shown in the center portion of the magnetic head 100 in FIG. 1. A well-known magnetoresistance effect (MR) element 101 is a spin valve magnetoresistance effect (SVMR) element. This spin valve magnetoresistance effect element 101 is typically formed from multiple deposited thin-film layers including a first magnetic layer, a nonmagnetic layer, a second magnetic layer, and an antiferromagnetic layer (not shown).
The magnetoresistance effect element 101 also has ends 101A, 101B connected to electrically conductive lead terminals 102A, 102B. Hard films 103A, 103B are placed under the lead terminals 102A, 102B and in contact with the magnetoresistance effect element 101. The magnetoresistance effect element 101, the lead terminals 102A, 102B, and the hard films 103A, 103B are electrically insulated on both the upper and lower sides by an insulating upper gap material 104 and a lower gap material 105. A top 104A of the upper gap material 104 and a bottom 105A of the lower gap material 105 are shielded by soft magnetic shields 106, 107, respectively.
Recently, there has been considerable demand for higher density recording in magnetic recording/reproducing equipment. To detect information (signal magnetic field) magnetically recorded at high densities by using the magnetic head 100, which is very sensitive, the width of the gap W1 between the shields 106, 107 was narrowed and the film thickness of the entire magnetic head 100 was thinned. However, the gap materials 104, 105 must maintain a specific film thickness to maintain its insulating characteristics, and forming thinner gap materials 104, 105 is difficult and costly.
Thus, referring now to FIG. 2, a known magnetic head 200 further narrows a gap width W2 without narrowing the gap material as disclosed in unexamined Patent Publication (Kokai) No. 9-28807. In the magnetic head 200, a magnetoresistance effect element 201 is electrically connected to an upper shield 206 and a lower shield 207, which also function as the lead terminals. This configuration eliminates the need for a gap material 204 between the shield 206 and insulating film 202A, and between shield 206 and insulating film 202B, and eliminates the need for gap material 205 between shield 207 and hard film 209A, and between shield 207 and hard film 209B to further narrow the gap width W2. This, in turn, enables a narrower gap to be fabricated.
The upper and the lower gap materials 204, 205 placed above and below the magnetoresistance effect element 201 are formed from electrically conductive materials. The insulating films 202A, 202B are provided on ends 201A, 201B of the magnetoresistance effect element 201.
Referring again to FIGS. 1-2, the flow direction of the sense current for magnetic head 100 is different from the flow direction of the sense current for magnetic head 200. In the magnetic head 100, the sense current flows from the lead terminal 102A through the magnetoresistance effect element 101 to the lead terminal 102B (or in the reverse direction) in a direction parallel to a generally planar surface 108 of element 101 (only shown in cross section) hereinafter xe2x80x9cplanar directionxe2x80x9d. In the magnetic head 200, the sense current flows from the upper shield 206 through the magnetoresistance effect element 201 to the lower shield 207 (or in the reverse direction) in a direction perpendicular to a surface 208 of the element 201, hereinafter xe2x80x9cperpendicular directionxe2x80x9d. The magnetic head 100, in which the sense current flows in the planar direction, is called a CIP (Current In Plane) magnetic head. The magnetic head 200, in which the sense current flows in the perpendicular direction, is called a CPP (Current Perpendicular) magnetic head.
Since the sense current in the CIP magnetic head 100 described above flows in the planar direction, this head cannot use an MR element, for example, that requires the sense current to flow in the perpendicular direction as in a tunnel magnetoresistance effect (TMR) element. In contrast, magnetic heads using CPP are expected to become popular because of the ability of the magnetic head 200 described above to use the TMR element and to narrow the gap W2 as described above. However, the magnetic head 200 leaks current at both ends 201A, 201B of the magnetoresistance effect element 201, and therefore has difficulty in producing an efficient flow in the perpendicular direction.
To control the magnetic domain of the magnetoresistance effect element 201, hard films 209A, 209B are formed on both ends 201A, 201B of the magnetoresistance effect element 201 for applying a longitudinal bias magnetic field (not shown). In this case, however, if the hard films 209A, 209B are electrically conductive materials, electrical shorts develop with the upper gap layer 204, which in turn lowers the yield.
To prevent shorts and current leakage, the conventional material forming the hard films 209A, 209B is a magnetic material that is insulating and has a coercive force (Hc) above a specific value, for example, 500 Oe (oersteds). However, this kind of magnetic material is difficult to accurately form on ends 201A, 201B of the magnetoresistance effect element 201. If a hard film does not have the required coercive force, the longitudinal bias magnetic field becomes unstable, and the signal magnetic field from the magnetic recording medium cannot be accurately reproduced.
Thus, a main object of the present invention is to provide an improved magnetoresistance effect magnetic head that does not have substantial leakage of current at the ends of the magnetoresistance effect element.
Another object of the present invention is to provide an improved magnetoresistance capable of applying a sufficiently stable longitudinal bias magnetic field to the magnetoresistance effect element.
Yet another of the present invention is to provide an improved magnetic recording/reproducing apparatus with the improved head.
These and other objects of the present invention are discussed or will be apparent from the detailed description of the invention.
In one aspect of the present invention, leakage currents in the ends of the magnetoresistance effect element can be suppressed by an insulating antiferromagnetic layer placed next to the ends of the element. When the magnetic layers are placed in contact with the antiferromagnetic layers, unidirectional anisotropic magnetic field is generated by the exchange coupling. The magnetic layers apply a stable longitudinal bias magnetic field to the magnetoresistance effect element. Thus, the bias application layer can apply the needed longitudinal bias magnetic field to the magnetoresistance effect element while maintaining an insulating property.
More specifically, a magnetoresistance effect magnetic head has a magnetoresistance effect element and a biasing portion for applying a longitudinal bias magnetic field to the magnetoresistance effect element on at least one end of the magnetoresistance effect element. The biasing portion includes an insulating antiferromagnetic layer and a magnetic layer in exchange coupling with the antiferromagnetic layer.
In another aspect of the present invention, a single antiferromagnetic layer can be provided above and below the magnetic layer to form a sandwich structure. Because the magnetic layer is sandwiched from the above and below by the insulating antiferromagnetic layers, a unidirectional anisotropic magnetic field stronger than the magnetic layer can be provided while also providing better insulation.